1. Field of the Invention
The present invention relates to a structure for mounting module substrates having an electronic circuit, such as a DC-DC converter power-supply circuit, on a motherboard.
2. Description of the Related Art
FIG. 12 is a schematic side view showing an example of a module substrate mounting structure. A module substrate 49 includes a circuit board 45 with a circuit pattern (not shown) thereon, and circuit components 46 (for example, a transformer and an IC) mounted on the circuit pattern.
A circuit pattern (not shown) is formed on a motherboard 50, and circuit components (not shown) are mounted thereon. The circuit patterns of the module substrate 49 and the motherboard 50 are electrically connected to each other via connecting members 48.
An example of the module substrate is a DC-DC converter device. The DC-DC converter device converts input DC voltage and current into output DC voltage and current that satisfies specified requirements. A plurality of such DC-DC converter devices 49 are sometimes used in response to requests for output voltage and current conforming to the specified requirements. In this case, for example, a plurality of DC-DC converter devices 49 are arranged side by side with a space D therebetween on the motherboard 50 in consideration of heat radiation efficiency, as shown in FIG. 11. These DC-DC converter devices 49 are connected in parallel or in series by a wiring pattern 51 provided on the motherboard 50 according to the specifications.
However, in order to arrange a plurality of DC-DC converter devices 49 side by side such that the space D is provided therebetween, the motherboard 50 must have a large mounting area that is at least equal to the sum of the area corresponding to the number of the DC-DC converter devices and the area corresponding to the space D. For this reason, it is difficult to reduce the size of the motherboard 50.
In order to overcome the problems described above, preferred embodiments of the present invention provide a module substrate mounting structure which allows a plurality of module substrates to be mounted on a motherboard with very high density.
According to a first preferred embodiment of the present invention, a module substrate mounting structure includes a motherboard having connecting pads disposed on the surface thereof, and a plurality of module substrates each having connecting terminals provided on the surface thereof, wherein the module substrates are stacked with a space therebetween on the motherboard, the connecting terminals of the module substrates are electrically connected to the connecting pads on the motherboard via connecting members, a plurality of connecting terminals are arranged along an edge portion of each of the module substrates, the module substrates are stacked such that the connecting terminals aligned with each other, a plurality of connecting pads are arranged on the surface of the motherboard in the direction of arrangement of the connecting terminals, a plurality of rows of the connecting pads are arranged to be sequentially offset from one another from the inside of a region on the motherboard where the module substrates are mounted toward the outside thereof, the connecting terminals of an upper module substrate of the module substrates are electrically connected to the row of connecting pads on the outer side of the row of connecting pads connected to the connecting terminals of a lower module substrate via the connecting members, the length of the connecting members increases as the position of the module substrate connected thereto is higher, and the connecting members connected to the upper module substrate project further than the connecting members connected to the lower module substrate.
In this case, since a plurality of module substrates are stacked on the motherboard, the component mounting density on the motherboard is greatly increased, compared with the case in which a plurality of module substrates are placed side by side on the motherboard.
By making the lengths of the connecting members to be connected to a plurality of module substrates different, the module substrates can be stacked without using a substrate supporting member having a special shape. For this reason, it is possible to mount a plurality of module substrates on the motherboard with very high density and at low manufacturing cost without increasing the number of components and the number of manufacturing processes.
Furthermore, since the connecting members connected to the upper module substrate project further than the connecting members connected to the lower module substrate, it is possible to prevent the connecting members of a plurality of module substrates from touching one another even when the module substrates are stacked.
According to a second preferred embodiment of the present invention, a module substrate mounting structure includes a motherboard having connecting pads disposed on the surface thereof, and a plurality of module substrates each having connecting terminals provided on the surface thereof, wherein the module substrates are stacked with a space therebetween on the motherboard, the connecting terminals of the module substrates are electrically connected to the connecting pads on the motherboard via connecting members, a plurality of connecting terminals are arranged along an edge portion of each of the module substrates, the module substrates are stacked on the motherboard and are sequentially offset from one another in the direction of arrangement of the connecting terminals so that the edge portions with the connecting terminals disposed thereon are aligned with one another, and the connecting pads to be electrically connected to the connecting terminals of the module substrates via the connecting members are located in the same row.
In this case, since the module substrates are stacked while being offset from each other in the direction of arrangement of the connecting terminals, it is possible to prevent the connecting members of a plurality of module substrates from touching one another even when the module substrates are stacked. Moreover, since the connecting members of the upper module substrate and the connecting members of the lower module substrate are arranged in the same row, it is possible to equally and easily check the connecting state between the connecting members of the upper module substrate and the connecting pads and the connecting state between the connecting members of the lower module substrate and the connecting pads.
According to a third preferred embodiment of the present invention, a module substrate mounting structure includes a motherboard having connecting pads disposed on the surface thereof, and a plurality of module substrates each having connecting terminals disposed on the surface thereof, wherein the module substrates are stacked with a space therebetween on the motherboard, the connecting terminals of the module substrates are electrically connected to the connecting pads on the motherboard via connecting members, a plurality of connecting terminals are arranged along an edge portion of each of the module substrates, the module substrates are stacked on the motherboard and are sequentially offset from one another in the direction of arrangement of the connecting terminals so that the edge portions with the connecting terminals disposed thereon are aligned with one another, a plurality of connecting pads are arranged on the surface of the motherboard in the direction of arrangement of the connecting terminals, a plurality of rows of the connecting pads are arranged to be sequentially offset from one another from the inside of a region on the motherboard, where the module substrates are mounted, toward the outside thereof, the connecting terminals of an upper module substrate of the module substrates are electrically connected to a row of connecting pads on the outer side of a row of connecting pads connected to the connecting terminals of a lower module substrate via the connecting members, and the connecting members connected to the upper module substrate project further than the connecting members connected to the lower module substrate.
In this case, since the module substrates are stacked while being offset from each other in the direction of arrangement of the connecting terminals, it is possible to prevent the connecting members of a plurality of module substrates from touching one another even when the module substrates are stacked. Moreover, since the connecting pads corresponding to the connecting members of the module substrates are placed in separate rows, the area of the connecting pads can be increased, compared with the case in which the connecting pads are arranged in the same row, and the distance between the adjoining connecting pads can be increased. This makes it possible to facilitate the formation of the connecting pads, and to increase the width of the connecting members without having to be concerned about contact between the connecting members of the module substrates.
Preferably, a lower-substrate recognition mark is provided in a portion of the lower module substrate which is exposed because the upper module substrate is arranged in an offset manner. The lower-substrate recognition mark makes it easy to confirm whether or not the lower module substrate is mounted.
According to a fourth preferred embodiment of the present invention, a module substrate mounting structure includes a motherboard having connecting pads provided on the surface thereof, and a plurality of module substrates each having connecting terminals disposed on the surface thereof, wherein the module substrates are stacked with a space therebetween on the motherboard, the connecting terminals of the module substrates are electrically connected to the connecting pads on the motherboard via connecting members, a plurality of connecting terminals are arranged along a pair of edge portions of each of the module substrates, and the module substrates are stacked with the space therebetween on the motherboard so that the directions of arrangement of the connecting terminals of the upper and lower module substrates are nearly perpendicular to each other.
In this case, it is possible to prevent the connecting members of a plurality of module substrates from touching one another even when the module substrates are stacked.
Preferably, the module substrates have a nozzle suction area which is drawn by a component-transporting suction nozzle. This allows the module substrates to be transported by the suction nozzle in a reliable manner.
Preferably, the ratio of the length to width of the module substrates is within the range of about 1/3 to about 1/1. In this case, the module substrates can be transported in a stable manner by, for example, a suction nozzle. In particular, when the module substrates are stacked so that the directions of arrangement of the connecting terminals of the upper module substrate and the lower module substrate are nearly perpendicular to each other, the area of the overlapping portion therebetween can be increased by setting the ratio of the length to width within the above range.
Preferably, the module substrates have a converter power-supply circuit. When the module substrates have a converter power-supply circuit, a plurality of converter power-supply circuits are sometimes connected in series or in parallel for use. In such a case, a plurality of converter devices can be mounted in a region having an area substantially similar to that of a region for mounting a single converter device. That is, it is possible to mount a plurality of converter devices on the motherboard with high density, and to thereby reduce the size of the motherboard.
Further elements, characteristics, features, and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the attached drawings.